Semiconductor devices may be used in a variety of electronic devices, including, for example, personal computers, cell phones, digital cameras, tablets, and numerous other electronic devices. Semiconductor devices are typically fabricated by sequentially depositing insulating or dielectric layers, conductive layers, and semiconductive layers of material over a semiconductor substrate, and then patterning the various layers to form circuit components and elements thereon.
As technology progresses, the demand for smaller and smaller semiconductor devices with improved performance is increasing. Unfortunately, however, the scaling down of semiconductor devices has resulted in other problems. For example, as feature size decreases, resistance increases, and an RC time delay (defined as the product of the chip equivalent resistance (R′) and the equivalent capacitance (C′)) limits the propagation delay. With scaling, an increasing portion of the chip equivalent resistance and capacitance is composed of metal resistance (R) and interlayer dielectric (ILD) contributed capacitance (C). To reduce the overall time delay, low dielectric constant materials may be used as insulating materials, and copper (Cu) may be used as an interconnect material.
Various methods have been proposed for growing larger Cu grains or controlling grain growth in damascene interconnect structures.